Buster Posey tries to convince umpire Ron Kulpa that he hadn't struck out in the fifth.

Photo: Eric Risberg, Associated Press

Buster Posey tries to convince umpire Ron Kulpa that he hadn't...

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SAN FRANCISCO, CA - JULY 03: Buster Posey #28 of the San Francisco Giants talks to pitcher Madison Bumgarner #40 after the St. Louis Cardinals scored three runs in the fourth inning at AT&T Park on July 3, 2014 in San Francisco, California. (Photo by Ezra Shaw/Getty Images)

Photo: Ezra Shaw, Getty Images

SAN FRANCISCO, CA - JULY 03: Buster Posey #28 of the San Francisco...

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Madison Bumgarner helps himself with a run-scoring single in the third.

Photo: Ezra Shaw, Getty Images

Madison Bumgarner helps himself with a run-scoring single in the...

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SAN FRANCISCO, CA - JULY 03: Jason Motte #30 of the St. Louis Cardinals pitches against the San Francisco Giants in the ninth inning at AT&T Park on July 3, 2014 in San Francisco, California. (Photo by Ezra Shaw/Getty Images)

Photo: Ezra Shaw, Getty Images

SAN FRANCISCO, CA - JULY 03: Jason Motte #30 of the St. Louis...

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SAN FRANCISCO, CA - JULY 03: Jason Motte #30 and Yadier Molina #4 of the St. Louis Cardinals high five one another after they beat the San Francisco Giants at AT&T Park on July 3, 2014 in San Francisco, California. (Photo by Ezra Shaw/Getty Images)

Photo: Ezra Shaw, Getty Images

SAN FRANCISCO, CA - JULY 03: Jason Motte #30 and Yadier Molina #4...

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SAN FRANCISCO, CA - JULY 03: Carlos Martinez #44 of the St. Louis Cardinals pitches against the San Francisco Giants at AT&T Park on July 3, 2014 in San Francisco, California. (Photo by Ezra Shaw/Getty Images)

Photo: Ezra Shaw, Getty Images

SAN FRANCISCO, CA - JULY 03: Carlos Martinez #44 of the St. Louis...

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SAN FRANCISCO, CA - JULY 03: Brandon Crawford #35 of the San Francisco Giants leaps to try to catch a ball thrown wide by first baseman Adam Duvall #37 on a double play attempt in the fourth inning of their game against the St. Louis Cardinals at AT&T Park on July 3, 2014 in San Francisco, California. (Photo by Ezra Shaw/Getty Images)

Photo: Ezra Shaw, Getty Images

SAN FRANCISCO, CA - JULY 03: Brandon Crawford #35 of the San...

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San Francisco Giants manager Bruce Bochy, left, and hitting coach Hensley Meulens, right, rest on the dugout railing in the ninth inning of their baseball game against the St. Louis Cardinals, Thursday, July 3, 2014, in San Francisco. St. Louis won the game 7-2. (AP Photo/Eric Risberg)

Photo: Eric Risberg, Associated Press

San Francisco Giants manager Bruce Bochy, left, and hitting coach...

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St. Louis Cardinals manager Mike Matheny, left, visits with San Francisco 49ers head coach Jim Harbaugh, right, in the dugout after their baseball game against the San Francisco Giants Thursday, July 3, 2014, in San Francisco. St. Louis won the game 7-2. (AP Photo/Eric Risberg)

Photo: Eric Risberg, Associated Press

St. Louis Cardinals manager Mike Matheny, left, visits with San...

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St. Louis Cardinals' Jon Jay, followed by Matt Holliday celebrate with their teammates at the end of their baseball game against the San Francisco Giants Thursday, July 3, 2014, in San Francisco. St. Louis won the game 7-2. (AP Photo/Eric Risberg)

Photo: Eric Risberg, Associated Press

St. Louis Cardinals' Jon Jay, followed by Matt Holliday celebrate...

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St. Louis Cardinals starting pitcher Carlos Martinez dives for a bunt ground ball hit by the San Francisco Giants' Gregor Blanco in the fifth inning of their baseball game Thursday, July 3, 2014, in San Francisco. Blanco got a single on the play. (AP Photo/Eric Risberg)

Photo: Eric Risberg, Associated Press

St. Louis Cardinals starting pitcher Carlos Martinez dives for a...

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St. Louis Cardinals' Seth Maness, right, is tagged out at home plate by San Francisco Giants catcher Buster Posey, left, in the eighth inning of their baseball game Thursday, July 3, 2014, in San Francisco. Maness was trying to score from third base after the Cardinals' Jhonny Peralta lined into a double play to Giants left fielder Tyler Colvin. (AP Photo/Eric Risberg)

Photo: Eric Risberg, Associated Press

St. Louis Cardinals' Seth Maness, right, is tagged out at home...

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San Francisco Giants' Hunter Pence strikes out swinging against St. Louis Cardinals starting pitcher Carlos Martinez in the third inning of their baseball game Thursday, July 3, 2014, in San Francisco. (AP Photo/Eric Risberg)

Photo: Eric Risberg, Associated Press

San Francisco Giants' Hunter Pence strikes out swinging against St....

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From left to right, San Francisco Giants pitching coach Dave Righetti, starting pitcher Madison Bumgarner and catcher Buster Posey stand on the mound after a talk in the fourth inning of a baseball game against the St. Louis Cardinals, Thursday, July 3, 2014, in San Francisco. (AP Photo/Eric Risberg)

Photo: Eric Risberg, Associated Press

From left to right, San Francisco Giants pitching coach Dave...

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St. Louis Cardinals' Jon Jay, right, is greeted by teammate Mark Ellis, left, after scoring the Cardinals' fifth run in the fourth inning of a baseball game against the San Francisco Giants, Thursday, July 3, 2014, in San Francisco. Ellis and Jay both scored on the play after Carlos Martinez singled on a ground ball to left field. (AP Photo/Eric Risberg)

Photo: Eric Risberg, Associated Press

St. Louis Cardinals' Jon Jay, right, is greeted by teammate Mark...

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St. Louis Cardinals starting pitcher Carlos Martinez throws in the first inning of their baseball game against the San Francisco Giants Thursday, July 3, 2014, in San Francisco. (AP Photo/Eric Risberg)

Photo: Eric Risberg, Associated Press

St. Louis Cardinals starting pitcher Carlos Martinez throws in the...

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San Francisco Giants starting pitcher Madison Bumgarner throws in the first inning of their baseball game against the St. Louis Cardinals Thursday, July 3, 2014, in San Francisco. (AP Photo/Eric Risberg)

On June 5, the world was the Giants' oyster. They flew home after a satisfying series win at Cincinnati with an 8 1/2-game lead in the National League West and a schedule to die for - 20 of their next 25 games at home.

The Giants could have stepped on the Dodgers' throats. Instead, the stretch left them gasping for air.

The Giants lost 17 of the 25, and a division lead that grew to 9 1/2 games with a sweep of the Mets disappeared, along with the fiction that they were the best team in the league.

The enviable portion of their schedule ended dismally with Thursday's 7-2 loss. The Giants were outscored 42-19 in an embarrassing 2-8 homestand against the Padres, Reds and Cardinals, with Tim Lincecum authoring both victories.

"We're too good to have a homestand like that," manager Bruce Bochy said after conferring with general manager Brian Sabean and select players to discuss the team's plight. "To come home and struggle like we did, I don't think that's something that anybody saw coming. We know it's not acceptable.

"There's a time to say, 'Enough is enough.' That's where we're at. ... Part of it is getting mad at what's happened here and doing something about it. We've just got to do that. You've got to do it yourself, including myself, everybody. That's the best approach."

The last loss on the homestand was the ugliest.

Madison Bumgarner allowed five runs (four earned) in five innings. He spotted St. Louis a 2-0 lead on Jhonny Peralta's first-inning home run and could not limit the damage after a throwing error by rookie first baseman Adam Duvall in a three-run fourth.

Duvall fielded what should have been an inning-ending double-play groundball by Mark Ellis and airmailed his throw to center field. Bumgarner then surrendered a Jon Jay double for one run and a two-run single past a drawn-in infield by pitcher Carlos Martinez.

After the game, the Giants optioned Duvall to Triple-A Fresno to clear room for Brandon Belt, who returns Friday.

Meanwhile, a new-look lineup with Hunter Pence leading off barely dented the scoreboard. The only Giant with an RBI was Bumgarner; the ninth spot in the Cardinals' lineup outhit the Giants' 1 through 5 hitters 3-2.

Buster Posey had a shot to get the Giants back into a 5-1 game when he batted with the bases loaded and two outs in the fifth. Martinez, armed with a 99 mph fastball, fanned Posey on an 87 mph slider.

The Giants are pinning a lot of hope on Belt, who will bat second in San Diego on Friday when he rejoins the team after eight weeks of recovery from a broken thumb.

Whether he likes it or not, Belt will carry the expectations of an offensive savior.

"I've dealt with a lot the last couple of years," Belt said. "I know how to be even-keeled right now. I've got to do my job. I'm not going to put too much pressure on myself. I'm going to do what I'm supposed to do. Hopefully the rest of the team will do the same."

With or without Belt, the Giants had a chance to win the West the easy way. Now, talk of a division title seems oddly hollow for a squad that started Thursday in first place.

The Giants have to win it the hard way. They have completed roughly 60 percent of their home schedule and will play 44 of their final 76 games on the road, including 22 of the next 33.

AWOL offense

Even when the Giants pitched well during the 2-8 homestand, the offense provided little help. Only once in the 10 games did the Giants reach double digits in hits - and that came in Tim Lincecum's June 25 no-hitter. The team hit .192 during the stretch and 29 of its 61 hits came from three players (Buster Posey 11, Hunter Pence 10 and Pablo Sandoval eight).